Unless controlled, the water in swimming pools, spas, hot tubs, and the like can become contaminated with algae and similar organisms. The contaminant growth is usually controlled by the addition of chlorine to the water. The amount of chlorine required to maintain the water in a substantially organism-free state depends on the size of the pool or spa, the climatic conditions, the temperature of the water, and the extent of use of the pool or spa. The hot water found in spas and hot tubs necessitates the frequent addition of chlorine, because the material added rapidly loses effectiveness. A device that can be placed in the water to dispense chlorine in controlled amounts relieves the spa owner of the necessity of regularly monitoring and maintaining the chlorine content of the water.
Chlorine dispensing devices exist for swimming pools. One such device, among many, is the Rainbow Plastics Model 330 floating dispenser for solid chlorine. This dispenser resembles an inverted hollow truncated cone. The interior serves as a receptacle into which granular pellets of water-soluble chlorine material are placed. Around the circumference of the receptacle adjacent to the bottom there are apertures consisting of elongated vertical slots. The slots cooperate with a similarly slotted sleeve around the exterior of the container. The sleeve can be adjusted so that the slots are fully closed, fully opened, or in between. The top of the receptacle is closable by a lid. The walls of the container are hollow and are filled with closed-cell plastic foam. The cavity in which the foam is located is hermetically sealed. When filled with a soluble solid source of chlorine or bromine ions and floated in a swimming pool, the pool water contacts the source material in the receptacle to dissolve the source material, thereby releasing the active constituent of the material into the water. The rate at which such solution and release occurs is regulated by the extent to which the apertures in the receptacle are opened or closed by the position of the adjustment sleeve on the exterior of the receptacle. This dispenser is not conveniently usable in a spa because the effective size of the apertures cannot be regulated precisely enough to prevent the dispenser from over-chlorinating the spa water which, by reason of its temperature, acts more rapidly on the source material than the usually cooler water in a swimming pool. Also, this dispenser has a relatively large capacity for containing the source material so that, even when its apertures are very nearly closed, substantial quantities of source material are wetted and dissolved.
Other prior art products include cumbersome floating structures, each receiving a non-openable replaceable cartridge that contains the slowly soluble source of chlorine or other halogen. The exterior of the cartridge contains ribs which cooperate with the slots in the large float to hold the cartridge in a selected position vertically relative to the float. The containers are molded with bumps axially spaced along the container adjacent to the bottom end and a single bump adjacent to the top end. The user cuts off one or more bottom bumps to define the extent to which water communicates with the inside of the container, and cuts off the top bump to provide air communication to the inside of the container. The container is then placed into the large float and the resulting assembly is placed in the pool. Water then fills the cartridge to the waterline of the floating assembly; the vertial position of the cartridge in the float determines the extent to which the cartridge contents are wetted.
There are several practical difficulties with these last products. They are quite large and so do not fit well into a spa or hot tub. Their size makes them cumbersome to remove from the spa when the spa is to be used. They are aesthetically unappealing. They cannot reliably be adjusted to provide the precise solution rates needed for efficient chlorination (halogenation) of spas and hot tubs because of the crude and imprecise manner in which communication of water to the interior of the cartridge is provided. The are essentially floating packages of halogen source material designed by major source material manufacturers whose purpose is to market source material; the user cannot change source material without changing the entire dispenser; the user cannot use any source material he wishes.
In a dispenser for spas, it is important that the rate of solution of the source material be precisely controllable over a range commensurate with the lower chlorination requirements of spas as compared to swimming pools. The dispenser should not be too bulky so as not to create an obstruction in the spa. The dispenser should enable the user to select, as he chooses, from among many commercially available source materials. Finally, the dispenser should be made of a material resistant to damage from prolonged exposure to sunlight and chemicals.